Sat Comm Sys Engineering

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philiptraversTypewritten Text

2 Satellite Engineering Research Corporation

OutlinePART 1: THE SPACECRAFT AND ITS ORBIT1. Mission Analysis2. Transfer Orbit3. Orbital Perturbations and Stationkeeping4. The Spacecraft Environment5. Earth-Satellite Geometry 6. Constellation Design

PART 2: PRINCIPLES OF SATELLITE COMMUNICATION7. Signals and Spectra8. Analog Modulation9. Digital Modulation

10. Coding11. The Electromagnetic Spectrum12. The RF Link13. Earth Stations14. Multiple Access15. Antennas 16. System Temperature17. Polarization 18. Rain Loss

PART 3: APPLICATIONS TO SATELLITE COMMUNICATION SYSTEMS19. Link Budgets for Geostationary Satellites20. Link Budgets for Nongeostationary Satellites


The RF Link(Excerpt)


Antenna pattern, beamwidth, and gain

Beamwidth shows size of beam.

Gain shows relative strength of radiation. The maximum (boresight) gain is

Gain and beamwidth are linked: As the gain increases, the beamwidthdecreases, and vice versa.

2

2 2

4 4 29,000 4*A

DG A = = = = =

HPBW 70kD D = = =

= half powerbeamwidth

sidelobes main lobe

3 dB pointsgain G

AD

An isotropic antenna radiates equally in all directions like a light bulb = 4

A = total solid angle of radiation = solid angle between HP points

where *, , = measures of antenna efficiency

where k = antenna taper factor


Example: Earth terminal antenna

Ku band downlink frequencyf = 12 GHz

8

9

3 10 m/s 0.025 m12 10 Hz

cf

= = =

0.025 mHPBW 70 70 0.355.0 mD

= = = =

22 5.0 m0.60 237,0000.025 m

DG = = =

10[ ] 10 log (237,000) 53.7 dBG = =Prime Focus Feed; 5 meter reflector; Tx and Rx

C-Band gain 46 dB; Beamwidth = 1oKu-Band gain 54 dB; Beamwidth = 0.4o


Equivalent isotropic radiated power (EIRP)The equivalent isotropic radiated power (EIRP) is the transmit power of a hypothetical antenna radiating equally in all directions (like a light bulb) so as to have the same power flux density over the coverage area as the actual antenna.

The power flux density of the actual antenna is

where * is the antenna power loss efficiency, P = * Pin is the transmitted power, S is the total coverage area at distance d, A is the antenna beam solid angle, and Gt = * (4 / A ) is the transmit gain.

By the definition of EIRP

Therefore,

2 2 2

44

* *4

in in int

A A

P P PP GS d d d

= = = =

2

EIRP4 d =

EIRP t inG P=The EIRP is the product of the antenna transmit gain and the power applied to the inputterminals of the antenna. The antenna efficiency * is absorbed in the definition of gain.


Example 1

numeric form logarithmic (dB) form

Gt = 100 [Gt] = 10 log10(100) = 20.0 dB

Pin = 50 W [Pin] = 10 log10 (50 W) = 17.0 dBW

EIRP = Gt Pin [EIRP] = [Gt] + [Pin]

= (100)(50 W) = 20.0 dB + 17.0 dBW

= 5000 W = 37.0 dBW

10 log10(5000 W) = 37.0 dBW


Example 2

[PHPA] = 10 log10(100 W) = 20 dBW

[Pin] = [PHPA] [L] = 20 dBW 1 dB = 19 dBW

[EIRP] = [Gt] + [Pin] = 60 dB + 19 dBW = 79 dBW


Figure of Merit (G / T)

The ratio of the receive antenna gain G to the total system temperature T is called the figure of merit.

[ G / T ] = [ G ] [ T ] (dB/K)

where[ G ] = receive antenna gain (dB)

[ T ] = total system temperature (dBK)

The figure of merit is independent of the point where it is calculated. However, the gain and system temperature must be specified at the same point.

Example: Suppose the antenna gain is 53.7 dB and the system temperature is 150 K. Then

[ T ] = 10 log10(150 K) = 21.7 dBK

[ G / T ] = [ G ] [ T ] = 53.7 dB 21.7 dBK = 32.0 dB/K


Satellite communications payload architecture


Transponder


Satellite transponder frequency plan (C-band)

Typical satellite data

EIRP (dBW) C-band

Ku-band

CONUS 38.8 48.3

Alaska 33.7 39.1

Hawaii 33.8 46.4

Puerto Rico/U.S. Virgin Islands 34.0 44.9

Mexico 35.9 43.6

Southern Canada 37.0 44.3

Caribbean 34.3 43.4

G/T (dB/K) C-band

Ku-band

CONUS 0.4 1.2

Alaska -8.2 -5.9

Hawaii -5.2 0.6

Puerto Rico/U.S. Virgin Islands -3.7 0.7

Mexico -3.5 -3.5

Southern Canada -2.3 -0.6

Caribbean -3.5 -2.3

100 W nominal27 MHz24 Ku-band

100 W nominal54 MHz4 Ku-band

20 W nominal36 MHz24 C-band97 degrees W

PowerUseable Bandwidth

TranspondersOrbital Location

Saturation Flux Density - Typical CONUS-71 to -92 (dBW/m) at C-band adjustable in 1 dB steps

-75 to -96 (dBW/m) at Ku-band adjustable in 1 dB steps

PolarizationOrthogonal linear polarization at C-band and Ku-band.

Frequency Band4/6 GHz and 12/14 GHz

Ku-band Optional "Automatic Level Control" ModeMitigates the effects of uplink rain fade by maintaining the transponder at a specific fixed operating point between saturation and 8 dB input backoff.

Telstar 5 97 W C/Ku bandBegan service: 7/ 97

Transponders: 24 C-band @ 36 MHz4 Ku-band @ 54 MHz

24 Ku-band @ 27 MHz

Coverage: Continental US, Alaska, Hawaii, Puerto Rico, the Caribbean, and into Canada and Latin America.

Markets: Strong broadcast and syndication neighborhood anchored by ABC and FOX; host to SNG, data, business television, Internet, direct-to-home programming and digital data applications

Station-keeping 0.05 degreesMission Life 12 years



Satellite EIRP footprint

P = 100 W [ P ] = 20 dBW [ G ] = 30 dB

[ EIRP ] = [ G ] + [ P ] = 30 dB + 20 dBW = 50 dBW (COC)


Satellite Figure of Merit G / T

T = 630 K [ T ] = 28 dBK [ G ] = 30 dB

[ G / T ] = [ G ] [ T ] = 30 dB 28 dBK = 2 dB/K (COC)

Earth-satellite geometryCity/Country Latitude W Longitude Azimuth Elevation

Anchorage, AK/USA 61.22 149.90 123.52 8.3

Boston, MA/USA 42.21 71.03 215.82 34.6

Calgary/Canada 51.08 114.08 158.45 29.3

Dallas, TX/USA 32.46 96.47 180.37 52.2

Guatemala City/Guatemala 14.63 90.52 204.71 71.2

Halifax/Canada 44.65 63.60 223.21 28.8

Havana/Cuba 23.12 82.42 213.52 58.3

Honolulu, HI/USA 21.32 157.83 101.44 18.8

Houston, TX/USA 29.45 95.21 183.28 55.6

Jacksonville, FL/USA 30.19 81.39 208.53 50.9

Los Angeles, CA/USA 34.03 118.14 145.36 44.4

Merida/Mexico 20.97 89.62 199.81 64.0

Mexico City/Mexico 19.42 99.17 173.65 67.1

Miami, FL/USA 25.46 80.11 214.78 54.8

Nassau/Bahamas 25.08 77.33 220.17 53.3

New York, NY/USA 40.43 74.01 213.10 37.6

Reno, NV/USA 39.53 119.82 146.53 38.5

San Francisco, CA/USA 37.46 122.25 142.19 39.1

San Juan/Puerto Rico 18.48 66.13 242.07 48.8

Seattle, WA/USA 47.60 122.33 147.34 30

Toronto/Canada 43.70 79.42 204.71 36.6

Vancouver/Canada 49.22 123.10 147.10 28.3

Washington, DC/USA 38.53 77.02 210.99 40.7

Telstar 5 97 W C / Ku band

cos cos coscos(34.03 )cos(118.14 97.0 )0.7730

= = =

39.38 = sinsinsin

sin(118.14 97.0 )sin(39.38 )

0.5685

Az =

= =

180 34.64 145.36Az = = cos /tan

sincos(39.38 ) (6378 km) /(42,164 km)

sin(39.38 )0.9799

ER r =

= =44.42 =

Example: Earth terminal in Los Angeles



Free space loss

The free space loss takes into account that electromagnetic waves spread out into spherical wavefronts as they propagate through space due to diffraction.

For a geostationary satellite, the free space loss is on the order of 200 dB (or a factor of 1020).

The received power at the earth terminal is typically on the order of tens ofpicowatts.

2 24 4s

d d fLc

= = 2

10 104 4[ ] 10 log 20logs

d dL = =


ExampleProblem: Determine the free space loss for a Ku band downlink between Telstar 5 at 97W Longitude and Los Angeles if the frequency is 12 GHz and the angle of elevation is 44.4.Solution: The wavelength is

The slant range is

Thus

8

9

3 10 m/s 0.025 m12 10 Hz

cf

= = =

2 2

2 2

( cos ) sin

(42,164 km) (6378 km cos44.4 ) 6378 km sin 44.4

37,453 km

E Ed r R R = = =

RE = Earths radiusr = orbit radius

= elevation angle

2 2200004 4 37,453, m 3.544 10

0.025 msdL

= = = 20

10[ ] 10 log (3.544 10 ) 205.5 dBsL = =


Received carrier powerReceived carrier power

ee

A PC AS L

= = Footprint areaTransmit gain

24*t

dSG=24 4* *t

A

dGS

= =Receiver equivalent areaReceive gain

2

4r eG A

=

2

4e rA G =

Received carrier power

2

2 2

( )( / 4 ) EIRP14 / * (4 / )

t in rr r

t s

G P GG GPCd G L d L L L

= = =

24s

dL =

Free space lossEquivalent isotropic radiated power

EIRP t inG P=


Example

Problem: Determine the received carrier power for the Ku band downlink between Telstar 5 and an Earth terminal in Los Angeles if the frequency is 12 GHz and the antenna has an efficiency of 0.60 and a diameter of 5.0 m. Allow a rain attenuation loss of 1.9 dB, a gaseous atmospheric loss of 0.1 dB, and a pointing loss of 0.2 dB.

Solution: The satellite EIRP in Los Angeles is 49.2 dBW. At 12 GHz, the antenna gain is 53.7 dB and the free space loss is 205.5 dB. Therefore, the received carrier power is

Therefore,

[ ] [EIRP] [ ] [ ] [ ] [ ] [ ]

49.2 dBW 53.7 dB 205.5 dB

1.9 dB 0.1 dB 0.2 dB

104.8 dBW

r s r a pC G L L L L= + = +

=

10.48 1110 W 3.3 10 W 33 pWC = = =


Noise power

Thermal noise power in bandwidth B

where the spectral noise density is

for system temperature T and Boltzmanns constant is

0 BN N B k T B= =

0 BN k T=

[ ] 228.6 dBW / K HzBk = 231.381 10 W / K HzBk =


Link budget equation

Carrier powerEIRP r

s r o

GCL L L

=Noise power

0BN k T B N B= =Carrier to noise ratio

1 1 1 1 1EIRPs r o B

C GN T L L L k B

=

Carrier to noise density ratio

0

1 1 1 1EIRPs r o B

C C GBN N T L L L k

= =


Link budget equation (continued)

The link budget equation is expressed in logarithmic (dB) form as follows (dB values indicated by brackets):

0[ / ] [EIRP] [ / ] [ ] [ ] [ ] [ ]s r o BC N G T L L L k= + Uplink

0[ / ] [EIRP] [ / ] [ ] [ ] [ ] [ ]s r o BC N G T L L L k= + Downlink

at satellite E/S satellite

satelliteat E/S E/S

at uplink frequency

at downlink frequency


Combined uplink and downlink

Only thermal noise (Average White Gaussian Noise)

1 1 1

net up down

C C CN N N

= + (numeric)

Include interference

1 1 1 1

net up down

C C C CN N N I

= + + Noise power

0N N B=

0

1C CN N B

=


Power flux density

The EIRP of the uplink Earth station antenna must be adjusted to match an acceptable power flux density (PFD) at the satellite.

2 2

EIRP 1 1 EIRP 1 1PFD4 ( / 4 )r s rd L L L L L = = =

2[ ] [EIRP] [4 ] [ ] [ ]rd L L = or

2[ ] [EIRP] [ ] [ / 4 ] [ ] [ ]s rL L L =


Example

Problem: For an uplink between an Earth station in Washington, DC andTelstar 5, the EIRP is 79.0 dBW, the slant range is 37,722 km, the rain attenuation is 5.9 dB, and the antenna pointing loss is 0.2 dB. Determine the power flux density incident on the satellite.

Solution:

2[ ] [EIRP] [4 ] [ ] [ ]rd L L = { }21079.0 dBW 10 log 4 (37,722,000 m) 5.9 dB 0.2 dB=

289.6 dBW / m= This PFD is within the specifications for Telstar 5.

Saturation Flux Density - Typical CONUS

-75 to -96 (dBW/m) at Ku-band adjustable in 1 dB steps

Ku-band Optional "Automatic Level Control" ModeMitigates the effects of uplink rain fade by maintaining the transponder at a specific fixed operating point between saturation and 8 dB input backoff.


Example link budget

Satellite

Name Telstar 5

Longitude deg 97.0

Transponder bandwidth MHz 27.0

EIRP dBW 49.2

G/T dB/K 2.0

Signal architecture

Information bit rate Mbps 22.5

dBHz 73.5

Modulation QPSK

Coding V(7,1/2)

Bits per symbol 2

Code rate 1/2

Percentage of raised cosine filtering 20

Noise bandwidth MHz 22.5

Occupied bandwidth MHz 27.0

BER 0.00001

Eb/No (uncoded) dB 9.6

Coding gain dB 5.1

Eb/No (ideal) dB 4.5

Modem implementation loss dB 0.5

Eb/No (required) dB 5.0

C/No (required) dBHz 78.5


Example link budget (continued)Uplink

Link calculation

Frequency GHz 14.0

Wavelength m 0.0214

Earth station EIRP dBW 79.0

Satellite G/T dB/K 2.0

Free space loss dB 206.9

Rain region D2

Availability percent 99.95

Rain attenuation dB 5.9

Antenna pointing error deg 0.02

Antenna pointing loss dB 0.2

Boltzmann's constant dBW/K Hz -228.6

C/No (uplink) dBHz 96.6

Noise bandwidth dBHz 73.5

C/N (uplink) dB 23.1

Power flux density dBW/m2 -89.6

Earth station transmit terminal

City Washington

Longitude deg 77.0

Latitude deg 38.5

Earth central angle deg 42.7

Elevation angle deg 40.8

Slant range km 37722

HPA Power W 100.0

dBW 20.0

Antenna diameter m 9.2

Antenna half power beamwidth deg 0.16

Antenna efficiency 0.55

Antenna transmit gain dBW 60.0

Line loss dB 1.0

EIRP dBW 79.0


Example link budget (continued)Downlink

Link calculation

Frequency GHz 12.0

Wavelength m 0.025

Satellite EIRP dBW 49.2

Earth station G/T (clear sky) dB/K 32.0

Free space loss dB 205.5

Rain region F

Availability percent 99.95

Rain attenuation dB 1.9

Degradation in G/T dB 2.2

Gaseous atmospheric loss dB 0.1

Antenna pointing error deg 0.05

Antenna pointing loss dB 0.2

Boltzmann's constant dBW/K Hz -228.6

C/No (downlink) dBHz 99.9

Noise bandwidth dBHz 73.5

C/N (downlink) dB 26.3

Earth station receive terminal

City Los Angeles

Longitude deg 118.1

Latitude deg 34.0

Earth central angle deg 39.4

Elevation angle deg 44.4

Slant range km 37453

Antenna diameter m 5.0

Antenna half power beamwidth deg 0.35

Antenna efficiency 0.60

Antenna receive gain dB 53.7

Clear sky antenna noise temperature K 25

Receiver equivalent temperature K 125

System temperature K 150

dBK 21.8

G/T (clear sky) dB/K 32.0


Example link budget (continued)Combined uplink and downlink

C/N (uplink) dB 23.1

C/N (downlink) dB 26.3

C/I (adjacent satellite) dB 20.0

C/I (cross polarization) dB 24.0

C/N (net) dB 16.7

Noise bandwidrh dBHz 73.5

C/No (net) dBHz 90.3

Information bit rate dBHz 73.5

Eb/No (available) dB 16.7

Eb/No (required) dB 5.0

C/No (required) dBHz 78.5

Margin dB 11.7


Power levels in satellite link-30.0 dBW Output of modulator

and upconverter

Uplink path30.0 dB Driver gain20.0 dB Earth station HPA gain

1.0 dB Line loss60.0 dB Earth station antenna gain

6.1 dB Rain attenuation + other losses206.9 dB Free space loss

Satellite30.0 dB Satellite receive antenna gain69.0 dB Receiver amplifier gain57.0 dB Satellite TWTA saturated gain

2.0 dB Output losses29.2 dB Satellite transmit antenna gain

Downlink path205.5 dB Free space loss

2.2 dB Rain attenuation + other losses53.7 dB Earth station antenna gain

0.2 dB Line loss40.0 dB LNA gain35.0 dB Downconverter and

IF amplifier gain

-30.0 dBW Input to demodulator

To demodulator

Uplink

Transmitearth station

20.0 22.0

Earth StationEIRP = 79.0

-35.0

-134.0

Satellite

-104.0

-150

-100

-50

0

50

100PowerLevel (dBW)

Downlinkpath

-156.3 -158.5

Uplinkpath

72.9

Receiveterminal

-104.8

Frommodulator

-30.0Downlink

SatelliteEIRP = 49.2

20.019.0

-65.0

-30.00.0

-105.0


Antenna half power beamwidth

2

2

4 4 4*A

DG A = = = =

0 0

EIRP ( / )b t r in rb

s B s B

E G G P G TC RN N L L k T L L k

= = =

HPBW ck kD f D= = =

Antenna gain

Carrier to noise density ratio

2 24 4s

d d fLc

= =

= half power beamwidth = wavelengthf = frequency

c = speed of light

D = antenna diameter

k = antenna taper factor

*, , = antenna efficiency factorsA = antenna beam solid angled = slant range

S = footprint area

A = antenna area

C = carrier power

N0 = noise density

Rb = information bit rate

Eb = energy per information bit

EIRP = equivalent isotropic radiated power

Gt = transmit antenna gain

Gr = receive antenna gain

Pin = input power

Ls = free space loss

L = net attenuative loss

T = system noise temperature

kB = Boltzmanns constant

RF link (summary)

Free space loss

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